Four other men charged over the gang-rape face the death sentence if convicted in a special fast-track court, whose proceedings are subject to a media gagging order.

They have all pleaded not guilty.

A sixth 17-year-old suspect is being tried in a juveniles' court where he faces a maximum three-year imprisonment.

The victim, who was studying physiotherapy, died on December 29 at a hospital in Singapore, 13 days after the attack. As well as being repeatedly raped, she was also violated with a metal bar, leaving her with massive internal injuries.

'Drinking, abusing and getting into fights' ​Singh, a widower whose brother Mukesh is also an accused, was the regular driver of the white private bus alleged to have been used for the December 16 crime, which was normally used to ferry school children.

Police say Singh and friends enjoyed a meal together and were drinking heavily before they decided to take the bus out for a night-time joyride, picking up passengers who mistook the vehicle for genuine public transport.

Another senior police officer investigating the case, who asked not to be named, insisted that the suicide would not impact on the ongoing trial.

"The [court] case will continue. There is no reason for the case to suffer," said the officer, who also confirmed that Singh killed himself at 5.15am.

Another police officer deployed at Tihar Jail said Singh's body was taken to the government-run Deen Dayal Upadhyay hospital and his brother Mukesh was informed.

"We tried to save him and even employed revival techniques but failed," he said.

Singh, originally from western Rajasthan state, lived in a New Delhi slum called Ravi Dass colony where neighbours described him and his brother as rowdy and heavy drinkers.

"They were always drinking, abusing and getting into fights with us," one neighbour, who works as a domestic servant, said. – AFP

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The National Health Laboratory Services finally admitted to a bottleneck last week, after denying there were any issues since April. According to the service, the backlog of 80 000 tests started in the first week of May